On the basis of Mendel’s observations, predict the results from the following crosses with peas: (a) A tall (dominant and homozygous) variety crossed with a dwarf variety. (b) The progeny of (a) self-fertilized. (c) The progeny from (a) crossed with the original tall parent. (d) The progeny of (a) crossed with the original dwarf parent.

SouravSeptember 8, 2024

Answer

(a) A tall (dominant and homozygous) variety crossed with a dwarf variety

Cross: TT (tall, homozygous dominant) × tt (dwarf, homozygous recessive)

Results:

• Genotypes of Offspring: All progeny will have the genotype Tt.
• Phenotypes of Offspring: All progeny will exhibit the tall phenotype because the dominant allele (T) will mask the effect of the recessive allele (t).

(b) The progeny of (a) self-fertilized

Cross: Tt × Tt

Results:

• Genotypes of Offspring:
  • TT: 1/4 (25%)
  • Tt: 2/4 (50%)
  • tt: 1/4 (25%)
• Phenotypes of Offspring:
  • Tall: 3/4 (75%) (TT and Tt)
  • Dwarf: 1/4 (25%) (tt)

(c) The progeny from (a) crossed with the original tall parent

Cross: Tt (progeny of (a)) × TT (original tall parent)

Results:

• Genotypes of Offspring:
  • TT: 1/2 (50%)
  • Tt: 1/2 (50%)
• Phenotypes of Offspring:
  • All progeny will be tall because both genotypes (TT and Tt) result in the dominant tall phenotype.

(d) The progeny of (a) crossed with the original dwarf parent

Cross: Tt (progeny of (a)) × tt (original dwarf parent)

Results:

• Genotypes of Offspring:
  • Tt: 1/2 (50%)
  • tt: 1/2 (50%)
• Phenotypes of Offspring:
  • Tall: 1/2 (50%) (Tt)
  • Dwarf: 1/2 (50%) (tt)

These predictions are based on Mendel’s principles of segregation and dominance, which describe how alleles are inherited and expressed.